extruder motor not working

Hello, I am new here, I hope I put this in the right spot.
I have A mendelmax with ramps1.4 electronics and arduino 2560 ,and Marlin firmware..
I cannot get the extruder motor to run,I it runs fine when i plugged it into another set of axis pins,so it is not the motor itself.
The other axis motors run fine,however the y axis seems to "overstep",being that when I jog it 10 mm it advaces a little more than. 20 mm.
Which i wil have to change in the fimware when I get to that point,and get that figured out.
The question I have do you think the board is bad or maybe it needs to be turned on in the firmware?

While I am asking questions how do I get the firmware into the arduino editor,what file do I need to look for?

Marlin firmware is a collection of files, Don't just copy the pde file - copy the entire directory into the IDE sketchbook directory. I can't remember the organization of the subdirectories, but if you create a dummy project you can mimic the directory tree it creates.

Also, I'm not sure of the current state of this, but the Marlin I am using does not work with the 1.x Arduino IDE; I needed to load 0.23. If somehow you are using a version that will work in 1.0, then the pde file isn't the one you are looking for. Starting in 1.0, the Arduino IDE looks for a file extension of .ino for its main routine